repl: To exit, press ^C again or type .exit.

When the user hits `^C` in the REPL show more info about `.exit`.

The idea was to give more info to the user when they hit ^C.
Current version just displays `(^C again to quit)` and most
of the users are not aware of the `.exit` command that would
Exit the repl.

PR-URL: #3368
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/repl.js

@@ -355,7 +355,7 @@ function REPLServer(prompt,
         sawSIGINT = false;
         return;
       }
-      self.output.write('(^C again to quit)\n');
+      self.output.write('(To exit, press ^C again or type .exit)\n');
       sawSIGINT = true;
     } else {
       sawSIGINT = false;